1. Technical Field
Methods for forming capacitors of semiconductor devices, and more particularly, methods for forming capacitors are disclosed wherein the capacitors have a stacked structure of metal layer-insulating film-metal layer and having its storage electrode formed of ruthenium (hereinafter, referred to as xe2x80x9cRuxe2x80x9d), which provides improved formation rates of the Ru film having desired thickness using ozone (O3) having high reactivity.
2. Description of the Related Art
Generally, during the fabrication processed a capacitor having a storage electrode formed of Ru film, O2 gas is used as reaction gas of source materials for Ru films at a temperature ranging from 200 to 260xc2x0 C.
However, when Ru films are formed at the above temperature, oxygen or carbon atoms from the reaction gas penetrate into the Ru films. As a result, the Ru films become unstable.
In addition, in the subsequent process of forming dielectric films using tantalum oxide (Ta2O5), the oxygen atoms oxidize the TiN film used as lower barrier metal layer, which results in double capacitors or lifted-off of the storage electrodes formed of Ru.
In order to overcome the above problem, the oxygen is deoxidized to decrease the number of oxygen atoms penetrating into the Ru films during the fabrication process of Ru films, which results in prevention of the barrier metal layers being oxidized.
Any amine gas or its derivatives can be used as the reaction gas to deoxidize oxygen. When ammonia (NH3) gas is injected, the reaction mechanism is as follows:
O2+NH3xe2x86x922N2+6H2O.
However, since the reaction rate of the NH3 gas and oxygen gas is faster than that of the source material for Ru film and oxygen gas, decomposition of the source material for Ru film is inhibited and the formation rate of Ru film is reduced.
For example, when Ru film is formed at a thickness ranging from 100 to 500 xc3x85, with 0.01 to 1 cc/min of source material for Ru film, 10 to 100 sccm of oxygen gas and 100 to 1000 sccm of ammonia gas, formation time is increased from 10 to 30 minutes, thereby reducing the formation rate.
When the amount of oxygen gas in the reaction gas is increased to increase the formation rate of Ru films, step coverage is degraded and overhang occurs. In addition, the density of Ru film is decreased compared to Ru film only formed of Ru due to penetration of a large amount of oxygen atoms into Ru films. The oxygen atoms penetrated into Ru film also oxidize barrier metal layers during the subsequent heat treatment process, thereby deteriorating yield and characteristics of devices.
The above-described problems still exist even though the formation process of Ru films is performed at over 270xc2x0 C., and they are even more intensified when the amount of oxygen gas is decreased.
Improved methods for forming capacitors of semiconductor devices are disclosed wherein ozone gas having high reactivity is used as reaction gas during the formation process of Ru films to prevent reduction of the formation rate and the density of the Ru films and to further prevent oxidation of the barrier metal layer.
One disclosed method comprises:
forming a lower insulating layer comprising a contact plug including a barrier metal layer on a semiconductor substrate;
forming a Ru film electrically connected to the contact plug using O3 gas at a temperature ranging from about 300 to 350xc2x0 C.;
forming a dielectric film on the Ru film;
thermally treating the dielectric film; and
forming a plate electrode on the dielectric film.
It is preferable that the Ru film is used for storage electrodes.
It is preferable that the barrier metal layer comprises TiN.
It is preferable that the step of forming the Ru film is performed in amine gas atmosphere or selectively argon gas atmosphere.
It is preferable that the Ru film is performed using a material selected from the group consisting of tris(2,4-octanedionato)ruthenium, bis(ethylcyclopentadienyl)ruthenium [Ru(Etcp)2], (1,3-cyclohexadiene)ruthenium and combinations thereof as a source material for the Ru film.
It is preferable that the dielectric film, tantalum oxide material, is formed of tantalum ethylate [TA(OC2H5)5]. Here, the dielectric film is selected from the group consisting of BST((BaSr)TiO3) layer, PZT(PbZrTiO3) layer, SBT(SrBi2Ta2O9) layer, BLT(Bi(4-X)LaXTi3O12) layer, and combinations thereof.